ce: Calculate normalized sustainable yield

In ktmurray1219/mmrefpoints: Project Marine Mammal Populations and Calculate Reference Points

Description

This function calculates the normalized sustainable yield, which is used to find MNPL (the population size at which productivity is maximized).

Usage

ce(
  S0 = NA,
  S1plus = NA,
  AgeMat = NA,
  nages = NA,
  z = NA,
  E = NA,
  A = NA,
  P0 = NA,
  N0 = NA
)

Arguments

S0	Calf/pup survival, a numeric value between 0 and 1
S1plus	1+ survival rate for animals age 1 year and older, a numeric value between 0 and 1
AgeMat	Age at maturity (= age at first parturition - 1). Must be less than nages
nages	"maximum" age, treated as the plus group age. The plus group age can be set equal to the age at maturity +2 years without losing accuracy.
z	degree of compensation
E	bycatch mortality rate (applies to 1+ numbers)
A	the Pella-Tomlinson resilience parameter ((fmax - f0)/f0)
P0	unfished number-per-recruit - 1+ adults
N0	unfished numbers-per-recruit - mature adults

Value

a single value of normalized yield for exploitation rate E

Examples

# Set parameters
S0.w = 0.5; S1plus.w = 0.944; nages.w = 25; AgeMat.w = 18 
# Get number of individuals per recruit in terms of mature individuals (N0.w)
NPROut <- npr(S0 = S0.w, S1plus = S1plus.w, nages = nages.w, AgeMat = AgeMat.w, E = 0)

N0 <- NPROut$npr # mature numbers per recruit
# Get number of individuals per recruit in terms of individuals aged 1+ (P0.w)
P0 <- NPROut$P1r # 1+ nums per recruit

ce(S0 = S0.w, S1plus = S1plus.w, 
nages = nages.w, 
AgeMat = AgeMat.w, 
E=0.01, z=2.39,A=2, N0 = N0, P0 = P0)

ktmurray1219/mmrefpoints documentation built on Dec. 21, 2021, 8:40 a.m.